Decreased tear osmolarity and absence of the inferior marginal tear strip after sleep.

To better understand some of the clinical syndromes that patients experience on eyelid opening in the morning, we examined four patients clinically and measured tear osmolarity immediately after sleep and later in the day. The inferior marginal tear strip was absent, and tear osmolarity was at its nadir on eyelid opening after sleep. We propose a mechanism whereby decreased osmolarity, together with a probable decrease in tear volume, may increase lid-corneal and soft contact lens-corneal adhesion during sleep, and help explain both the development of recurrent corneal erosions on awakening and the tendency of soft contact lenses to adhere to the cornea overnight.